1
00:00:00,000 --> 00:00:02,820
[MUSIC PLAYING]

2
00:00:02,820 --> 00:00:07,530

3
00:00:07,530 --> 00:00:11,350
Congratulations on
completing another skill.

4
00:00:11,350 --> 00:00:16,000
Now it's time for a review
in the form of a quiz.

5
00:00:16,000 --> 00:00:18,120
As we go through
these questions,

6
00:00:18,120 --> 00:00:22,680
be sure to pause the video after
each question to give yourself

7
00:00:22,680 --> 00:00:25,470
the opportunity to answer
the question yourself

8
00:00:25,470 --> 00:00:27,930
before we then go
over the answer.

9
00:00:27,930 --> 00:00:33,200
That said, let's jump in
with our first question.

10
00:00:33,200 --> 00:00:37,210
Which of the following
would allow only prefixes

11
00:00:37,210 --> 00:00:39,880
that originated in AS 100?

12
00:00:39,880 --> 00:00:45,870

13
00:00:45,870 --> 00:00:47,700
So the main key
here, of course, is

14
00:00:47,700 --> 00:00:49,860
to remember that
it's originated.

15
00:00:49,860 --> 00:00:54,390
And we can say that it's AS 100,
but all of the answers are 100.

16
00:00:54,390 --> 00:00:56,440
So that doesn't really matter.

17
00:00:56,440 --> 00:00:58,320
So let's go down
each one of these

18
00:00:58,320 --> 00:01:00,250
and see what they look like.

19
00:01:00,250 --> 00:01:03,960
So answer number one, we have
a problem right off the bat,

20
00:01:03,960 --> 00:01:09,430
because it's using a name
here, and that's not supported.

21
00:01:09,430 --> 00:01:12,940
So that would make one
an incorrect answer.

22
00:01:12,940 --> 00:01:17,050
Number two, the formatting of
the access list is correct.

23
00:01:17,050 --> 00:01:20,670
However, if we look at
our regular expression,

24
00:01:20,670 --> 00:01:25,380
this has a caret, which
is beginning of string.

25
00:01:25,380 --> 00:01:28,480
That can't be at the end
of the string like this.

26
00:01:28,480 --> 00:01:31,950
So that would make
answer two incorrect.

27
00:01:31,950 --> 00:01:36,390
Number three, the formatting
is correct, again, of the ACL.

28
00:01:36,390 --> 00:01:39,160
We can see that all the rest
of the answers are the same.

29
00:01:39,160 --> 00:01:41,380
So we won't keep
discussing that.

30
00:01:41,380 --> 00:01:44,170
But let's look at the
regular expression.

31
00:01:44,170 --> 00:01:49,350
So first, it has to be preceded
by a space, then the 100,

32
00:01:49,350 --> 00:01:51,940
and then the end of string.

33
00:01:51,940 --> 00:01:54,000
So that's actually correct.

34
00:01:54,000 --> 00:01:55,770
That would work.

35
00:01:55,770 --> 00:01:57,840
Let's see what's wrong
with the rest of them,

36
00:01:57,840 --> 00:01:59,860
just for completeness.

37
00:01:59,860 --> 00:02:03,120
So the problem with
number four is that we

38
00:02:03,120 --> 00:02:06,660
have a dot instead of a space.

39
00:02:06,660 --> 00:02:12,120
Essentially what that means is
that 2100 would be acceptable

40
00:02:12,120 --> 00:02:14,520
here, or 90100.

41
00:02:14,520 --> 00:02:17,850
Any other number before the 100.

42
00:02:17,850 --> 00:02:21,930
And of course, we're supposed
to just be doing AS 100.

43
00:02:21,930 --> 00:02:26,070
So that's what would make
answer four incorrect.

44
00:02:26,070 --> 00:02:29,100
And number five, there's
not actually anything wrong

45
00:02:29,100 --> 00:02:30,120
with number five.

46
00:02:30,120 --> 00:02:32,430
It's saying, from the
beginning of the string,

47
00:02:32,430 --> 00:02:35,670
have 100, followed by a space.

48
00:02:35,670 --> 00:02:38,080
The only thing that
makes this incorrect is,

49
00:02:38,080 --> 00:02:41,310
again, we're supposed to
be looking at originated.

50
00:02:41,310 --> 00:02:44,550
And that would be at
the end of the AS path,

51
00:02:44,550 --> 00:02:46,540
not at the beginning of it.

52
00:02:46,540 --> 00:02:49,680
So five is formatted
correctly, it just

53
00:02:49,680 --> 00:02:52,750
doesn't match on what we
were told to match on.

54
00:02:52,750 --> 00:02:57,500
So that would make three
our only correct answer.

55
00:02:57,500 --> 00:02:59,120
Next question.

56
00:02:59,120 --> 00:03:01,370
Sort of a fill in the blanks.

57
00:03:01,370 --> 00:03:06,800
Define the meaning of each of
these special RegEx characters.

58
00:03:06,800 --> 00:03:12,590

59
00:03:12,590 --> 00:03:14,740
So let's go through
and write these in.

60
00:03:14,740 --> 00:03:16,450
First, we have the dot.

61
00:03:16,450 --> 00:03:22,030
This is going to be for
any single character.

62
00:03:22,030 --> 00:03:25,210
We have the unscore,
which would be a space,

63
00:03:25,210 --> 00:03:29,090
beginning of string,
or end of string.

64
00:03:29,090 --> 00:03:32,650
We have the pipe,
which means or.

65
00:03:32,650 --> 00:03:36,550
We have the caret,
which is begin string.

66
00:03:36,550 --> 00:03:40,450
The dollar sign, which
is the end of string.

67
00:03:40,450 --> 00:03:44,440
The parentheses
creates a grouping.

68
00:03:44,440 --> 00:03:47,860
The brackets create a set.

69
00:03:47,860 --> 00:03:54,760
The question mark is 0 or 1
instance of the preceding atom.

70
00:03:54,760 --> 00:03:59,140
The asterisk is 0
or more instances

71
00:03:59,140 --> 00:04:00,760
of the preceding atom.

72
00:04:00,760 --> 00:04:07,000
And the plus is one or more,
again, of the preceding atom.

73
00:04:07,000 --> 00:04:10,870
The backslash is an escape.

74
00:04:10,870 --> 00:04:12,820
This tells it to
escape the meaning

75
00:04:12,820 --> 00:04:15,380
of the character following it.

76
00:04:15,380 --> 00:04:17,750
So there's no right
or wrong answer here.

77
00:04:17,750 --> 00:04:19,510
But these are the
meanings of each

78
00:04:19,510 --> 00:04:22,820
of these special characters.

79
00:04:22,820 --> 00:04:24,320
Final question.

80
00:04:24,320 --> 00:04:30,410
What issue, if any, exists
for customers with destination

81
00:04:30,410 --> 00:04:32,960
based RTBH filtering?

82
00:04:32,960 --> 00:04:38,700

83
00:04:38,700 --> 00:04:41,360
Now, this being a fill
in the blank question,

84
00:04:41,360 --> 00:04:43,940
again, there'd be a couple
of ways to word this.

85
00:04:43,940 --> 00:04:47,780
But essentially, the
issue is that the customer

86
00:04:47,780 --> 00:04:52,760
or the destination, or you could
also refer to it as the victim

87
00:04:52,760 --> 00:04:57,380
network, will be unreachable
from the internet.

88
00:04:57,380 --> 00:04:59,630
And remember,
because of that, this

89
00:04:59,630 --> 00:05:02,390
is essentially helping
the distributed

90
00:05:02,390 --> 00:05:04,280
denial of service attack.

91
00:05:04,280 --> 00:05:07,700
But the idea here is that
it gives us the opportunity

92
00:05:07,700 --> 00:05:11,840
to contain the attack and
find a better solution that

93
00:05:11,840 --> 00:05:13,320
will work for the customer.

94
00:05:13,320 --> 00:05:17,480
And then we remove the
destination-based RTBH

95
00:05:17,480 --> 00:05:19,300
filtering.

96
00:05:19,300 --> 00:05:21,460
So that concludes this quiz.

97
00:05:21,460 --> 00:05:24,240
If you find you were missing
any of the information needed

98
00:05:24,240 --> 00:05:26,280
to answer these
questions, I would

99
00:05:26,280 --> 00:05:29,670
encourage you to go back and
review the sources referenced

100
00:05:29,670 --> 00:05:31,600
on each question.

101
00:05:31,600 --> 00:05:36,540
Otherwise, congratulations on
completing Exploring BGP Route

102
00:05:36,540 --> 00:05:38,190
Filtering Options.

103
00:05:38,190 --> 00:05:40,590
I hope this has been
informative for you,

104
00:05:40,590 --> 00:05:43,730
and I'd like to thank
you for viewing.

105
00:05:43,730 --> 00:05:47,000